1.The function of this ventilator is to keep the inside and outside pressure to be balanceable,even the inside temperature is under 0°C,so as to ensure free ipen of the door.With a tempere controller inside the window,if the temperature inside the coldroom is blow-40°C,which also keep the window's temperature within20-40°C,then guarantee fluent ventilation.

2.the size 170mm*170mm